This invention relates to snow and de-icing liquid removal from runway surfaces, and more particularly, it relates to a method and vehicular apparatus for traversing a surface to remove fluid such as snow and de-icing fluids therefrom.
With ever increasing air travel, there is greater pressure to fly aircraft during winter months which entails taking off and landing in snow storms. Taking off is particularly hazardous because of the extra weight of snow that can accumulate on the aircraft body and wings and interferes with lift. To minimize snow accumulation, the aircraft is sprayed with a de-icing or anti-icing liquid. The de-icing liquid is a glycol formulation composed of either ethylene or diethylene glycol and/or propylene glycol or similar material. Generally, there are two types of de-icing liquid. A first type of de-icing liquid (Type I), while effective in de-icing, has a formulation that does not adhere well to the aircraft surface. Thus, after application of the de-icing liquid, if the aircraft is required to stay on the ground for a period of time prior to takeoff, the de-icing liquid can have lost some of its effectiveness in keeping snow or ice from accumulating on the aircraft. To care for this problem, a second kind of de-icing liquid (Type II) is used. The second de-icing liquid has the capability of adhering to the aircraft up to a speed of 80 or 90 knots. The newer formulation, by clinging to the aircraft surface, can end up further out on the take-off runway, potentially creating a problem for subsequent aircraft taking off and landing. While two types of de-icing or anti-icing liquids are referred to herein, it will be understood that there are a number of types of de-icing and anti-icing liquids, and the invention described herein can be applied thereto. Further, de-icing and anti-icing is sometimes referred to interchangeably.
It is necessary to recover both de-icing formulations from the runway surface, or apron where the aircraft is sprayed, to meet environmental regulations and for safety concerns. By the use of "runway" or "runway surface" as used herein is meant to include the apron where the aircraft is sprayed with de-icing liquid. Thus, there is a great need to remove or recover the de-icing liquids economically.
However, the recovery of the liquid is complicated by the fact that it has to be recovered usually at freezing temperatures and that it is combined with snow and ice. Further, the second formulation has the additional problem that just as it is designed to cling to aircraft surfaces, it also clings to runway surfaces, making its recovery very difficult.
In prior attempts to recover the de-icing liquid, it has been found that brushing, sweeping or plowing snow combined with the de-icing liquid is largely ineffective because a residual amount of de-icing liquid remains on the runway surface. The residual amount is usually more than permitted by environmental regulations. Such regulations permit only a very low minimum amount, e.g., sometimes less than 5 mg/100 square centimeters in runoff water in some cases, to remain because the chemicals, e.g., glycols, eventually find their way to water supplies. Further, such recovery attempts are largely ineffective on packed snow or ice. Attempts at recovery of the de-icing liquids by vacuum also have been ineffective, particularly when the de-icing liquid is combined with snow or ice on the runway because the vacuum is not effective in removing ice or packed snow from the runway surface.
Many sweepers and machines are disclosed for cleaning paved surfaces. For example, U.S. Pat. No. 5,054,152 discloses a street sweeper that comprises side brushes, a pick-up brush and a conveyor mounted forward of the pick-up brush. The sweeper has a suspension component mounted forward of the rear axle which permits utilization of a standard production truck chassis. The disclosure of U.S. Pat. No. 5,054,152 is incorporated herein by reference.
U.S. Pat. No. 3,011,206 discloses a vehicle for cleaning streets wherein a scrubbing or sweeping brush is mounted on a chassis between the front and rear wheels of the vehicle, and while the vehicle is driven, the brush is rotated. In front of the rotary brush is a spraying or flushing mechanism which substantially consists of a pipe extending parallel to the brush. The pipe is connected to a fresh water supply and sprays powerful jets of water on the road along the length of the brush. A suction device is provided, and muddy water is drawn into a container by the effect of vacuum in the container.
U.S. Pat. No. 5,239,720 discloses a mobile surface cleaning machine that uses a sweeping-scrubbing apparatus including a sweeping brush for sweeping debris into a hopper and a one-piece squeegee for picking up solution after four staggered, disc brushes. The squeegee is U-shaped and has a longitudinal extent greater than that of the disc brushes located intermediate the legs of the squeegee. The squeegee has first and second blades that form a vacuum chamber to remove the cleaning solution.
U.S. Pat. No. 5,224,236 discloses a machine for cleaning paved surfaces to remove residues such as oil, grease and diesel fuel spills from streets. The machine has a water supply, recovery tanks and a steam generator for heating water from the supply tank to produce highly pressurized hot water and steam. A hose and wand are connected to the steam generator for directing pressurized water and steam against the surface to be cleaned. A pick-up wand is connected to a recovery tank having a vacuum pump for drawing water and residue from the surface.
U.S. Pat. No. 4,845,801 discloses a vehicle for cleaning surfaces with a first tank for storing cleaning liquid and a device for spraying a liquid at a first pressure and a first flow rate onto the surface to be cleaned. A device is provided for sucking the sprayed liquid towards a second tank. A second device is provided for moistening the surface to be cleaned with liquid at a second pressure and a second flow rate. The second pressure is lower than the first pressure and the second flow rate is lower than the first flow rate. The spraying and sucking devices are located at the rear of the vehicle, and the moistening device is located at the front of the vehicle. However, these machines are not effective for removing snow and/or ice and de-icing liquid combined therewith. Other street, surface or floor cleaning equipment is disclosed in U.S. Pat. Nos. 3,193,867; 3,447,188; 3,824,645; 4,023,233; 4,168,562; 4,369,540; and 4,845,801.
Thus, it will be seen that there is a great need for an apparatus and method for recovering de-icing liquids from surfaces such as runway surfaces when the de-icing liquid is combined with snow and ice. The present invention solves these problems and permits the effective removal of de-icing liquids from snow or ice-covered surfaces. Further, the present invention permits the recovery of the de-icing liquids in a way that aids economic processing and recycling of the de-icing liquid to recover the glycols therefrom.